MOLLUSC A. 



Animal soft, fleshy, furnished with a muscular coat 

 termed a mantle ; without any internal bony skeleton 

 supporting- jointed limbs, or external skeleton formed of 

 a hard ringed skin ; nervous system consisting of a number 

 of medullary masses distributed in different parts of the 

 body, one of the masses or ganglia placed over the gullet 

 and enveloping it like a collar. 



Molluscous animals, first separated as a Sub-kingdom 

 by Cuvier, have no skeleton like the Vertehrata, and no 

 jointed members like the Articulata ; they are, moreover, 

 known from the Radiata by their organs not radiating 

 from a common centre. They have a heart and blood- 

 vessels, a nervous system and breathing apparatus, and 

 they are covered by a soft mucous membrane, which is 

 named the mantle. The modifications exhibited in their 

 organization constitute the basis of the arrangement fol- 

 lowed in this work, which arrangement, although imper- 

 fect, may be termed the natural system. 



When the locomotive organs of the Mollusca are placed 

 in a circle round the head they form the Class Cepha- 

 lopoda ; when they swim by means of a pair of fins placed 



VOL. I. B 



